CSS problem with Netscape 4.76

I am new to CSS and am trying to implement them on a simple basis. I am using a simple linked style sheet with the single entry:
BODY { font-family: arial, sans-serif;
font-weight: bold;
font_size: 12 pt;
margin-left: 75px;
margin-right: 75px
}

The web page itself has tables.
IE 4 seems to have no problem with the CSS as is. With Netscape 4.76, the text within the table does not receive the style (the default font is displayed). If I remove the table (leaving the text), the proper style is applied, but Adding any additional formating (such as <big>, etc.) is ignored. If I leave the font-size out of the style, then I can change the size within the text.

Isn't the whole idea of "cascading" that the style is applied to lower tags (such as the <table>) and that the style can be locally overridden? Is this a Netscape proble or is there something I am doing wrong?

I followed the procedures to close this question, but something must have messed up. I appeciate all of the comments offered. Looking at the comments, and following some outside research, I have come to the conclusion that the various browsers implement CSS in such different ways that fully utilizing the power of this is "not ready for prime time". I have neither the time, patience or skill to write fully browser independent CSS entries that it is easier to avoid them until the standards are defined and followed among the browsers and independent code can be written.